Takata uses the chemical ammonium nitrate to cause a small explosion designed to inflate the air bags in a crash. But the inflators can explode with too much force when exposed to prolonged heat and humidity and hurl shrapnel into vehicles.

As many as 16 people have been killed worldwide and about 180 have been injured. Fiat Chrysler says it knows of no injuries involving this group of recalled vehicles.

Dealers will replace the inflators with parts made by another company. Fiat Chrysler says the parts are now available. Owners will receive letters starting January 12.